1. Field of the Invention
The present invention relates to a semiconductor inspection apparatus and a method of specifying attributes of dies on a wafer with such a semiconductor inspection apparatus.
2. Description of the Related Art
In the process of fabricating semiconductor circuit devices, it is customary to electrically test and evaluate a wafer before the wafer is cut into chips. In a parametric test using TEGs (Test Element Groups), one or more dies in a central area of the wafer where the probability of occurrence of defective dies is small are tested. If the tested die or dies in the central area of the wafer have no problem, then in peripheral areas of the wafer where probability of occurrence of defective dies is higher more or all dies are tested.
One example of a semiconductor parametric tester for use in such a test will be described below with reference to FIG. 7 of the accompanying drawings. As shown in FIG. 7, a semiconductor parametric test system 1 comprises a tester 3 for supplying an electric signal to a wafer 2 being measured and for measuring an electric signal from the wafer 2, a prober 5 for removing a wafer 2 to be measured from a wafer lot 4 and bringing probes into contact with a certain die on the removed wafer 2, a computer 6A for controlling the tester 3 and the wafer prober 5 to process measured data, and a group of measuring programs 6B for operating the computer 6A. The measuring program group 6B has a test plan 7 comprising an information file concerning the wafer 2 and devices fabricated thereon, a measuring algorithm library 8 comprising a file defining a measuring algorithm, a core program 9 for such functions as initializing various parts and loading and executing the test plan 7 and the measuring algorithm library 8, and a limit file 10. The measuring program group 6B also includes a user interface program 9a for receiving information from and giving information to the operator via a display unit and a keyboard. Each of the test plan 7, the measuring algorithm library 8, and the limit file 10 has a fill-in-the-box builder for the user to generate a file easily.
The test plan 7 includes a wafer specification 7a for defining the names, positions, and other attributes of dies on a wafer, a die specification 7b for defining the names and positions of modules on dies, a prober specification 7c for defining connections between device pads on the prober card in the wafer prober 5 and pins of a switching matrix, and a test specification 7d for defining a measuring algorithm for use in a device test.
For establishing the test plan 7, data concerning an entire wafer such as of the index and dimensions of the wafer and attributes of individual dies on the wafer are specified in the step of the wafer specification 7a. Dies refer to a plurality of chip regions produced on a semiconductor wafer. In many cases, dies in a peripheral area of a wafer are not used in the actual fabrication of semiconductor circuit devices, and are specified as marker dies for identifying other dies. Depending on the dimensions of the wafer and dies, such marker dies need to be manually specified. In addition, various tests, e.g., a DC conduction test, need to be specified as one of the attributes of predetermined dies. If a certain test fails, then a preliminary die may be required to be designated as a die to be tested next.
A die normally comprises several modules that are put together into a single set. The configuration of modules within individual dies is specified as the die specification 7b. The prober specification 7c is specified depending on the type of a probe card used for dies. A test to be conducted finally is specified as a measuring algorithm which is referred to as the test specification 7d. When the above data are specified to complete the test plan 7, the test plan 7 is loaded by the core program 9, and an actual test is carried out.
The parametric tester conducts a test of electric characteristics on a plurality of chip regions (dies) on a semiconductor wafer according to a die sorting test process. In this test, the probe of the wafer prober is held in contact with the dies. In recent years, as the yield of dies increases, not all the dies are tested, but only selected dies are tested, and if the tested dies are not defective, then the wafer is sent to a next fabrication process for increased productivity. The dies to be tested are selected in advance. Since defective dies tend to occur in the peripheral area of a wafer, many dies to be tested are selected in the peripheral area of the wafer. Therefore, it is not customary to place dies to be tested at equal intervals over the entire wafer.
When selecting dies on a wafer for a test, it has heretofore been difficult to select those dies particularly in the peripheral area of the wafer because of lack of suitable markers especially if the number of dies is large. It has been the conventional practice to display coordinate values at given distances or plot colors or patterns instead of graduations for assisting in selecting dies to be tested. Since such plotted assistive marks are mechanically applied, they fail to provide a useful relationship between different die layouts on individual wafers at the time when various types of semiconductor devices are manufactured on one production line, and hence are not effective enough as markers for complex die layouts particularly in the peripheral area of wafers.
Positional information relative to markers used for specifying dies to be tested has heretofore been managed as data of attributes different from data directly required for tests, indicative of whether dies are to be selected or not. The positional information thus managed as separate data is separate from the data required for the test, resulting in the need for data for associating these data with each other, which make the data management complex. For editing the data of the different attributes, because the data are managed separately, it is necessary to clearly indicate data to be edited, display the data on a display screen, and then edit the data in question, and to edit the data using tools that are different for individual data attributes. Accordingly, it has been tedious and time-consuming to edit data of different attributes. For example, a mode for selecting a die that serves as a marker and a mode for specifying a die to be tested may be different from each other, and these modes have to be switched for selecting and specifying dies.
Different data are displayed in an overlapping fashion on the same display screen. For example, 1) a die to be tested actually, 2) a die that serves as a marker in an editing process, 3) an initial position where an electric connection is to be made to a die by a wafer prober, and 4) a cursor on a die being presently edited, are displayed in an overlapping manner. However, data are prepared for each purpose of attributes and they are handled in a multiple mode only when displayed, and need to be edited separately for different attributes. For example, if a die to be tested is specified after a die that serves as a marker in the editing process is specified, then these specified dies are simultaneously displayed, but it is necessary to switch between modes in order to specify dies of different types.
The need for switching between modes makes it difficult for an operator who is not skilled enough to recognize how the testing process is in progress. The failure to recognize the proper testing sequence tends to cause errors.
It is therefore an object of the present invention to provide a unified management of data required for a test and information needed for specifying a die to be tested, so that data of different kinds can be handled together.
The present invention provides a means for managing multi-valued data of plural attributes for a die on a wafer in a unified manner, and displaying the managed data as graphical data and text data. The present invention also provides a means for editing the multi-valued data on a real-time basis based on the displayed data. More specifically, a method according to the present invention converts a plurality of data concerning individual dies on a wafer into data of at least three values, records the data of at least three values, and manages, in a unified manner, different attributes of dies, e.g., attributes indicating that dies are not specified, dies are specified as dies to be tested, and dies are specified as preliminary dies. The method also allows specified data to be immediately displayed on a display screen while a die is being specified.
According to the present invention, there is provided a method of specifying attributes of dies on a wafer in a semiconductor inspection apparatus comprising the steps of managing attribute data of dies as data of at least three values in a unified manner for selecting and specifying attributes of dies on a wafer from a plurality of attributes, allowing an operator to select any of the attributes of dies within one displayed image, and immediately reflecting selected attributes as die characteristics in the displayed image.
According to the present invention, there is also provided a semiconductor inspection apparatus comprising memory means for expanding and storing attribute data of dies as data of at least three values for selecting and specifying attributes of dies on a wafer from a plurality of attributes, and display control means for allowing an operator to select any of the attributes of dies within one displayed image, and reflecting selected attributes immediately as die characteristics in the displayed image.
The present invention applies to dies which have at least two attributes. If there exist two attributes for dies, then three values are required to express those attributes. Specifically, three values for a die indicate that only attribute A is specified, only attribute B is specified, and both attributes A, B are not specified (if both attributes A, B are to be simultaneously specified, then a fourth value is required). One of these attributes can be selected in one displayed image without the need for switching between modes. This is made possible by handling attribute data as multi-valued data such as a piece of data having at least three possible values. A selected attribute is immediately reflected in the displayed image when the attribute, once specified, is displayed on the display screen without the need for switching between modes. The display screen is not limited to a CRT or liquid crystal display screen, but represents a general display screen capable of presenting data to the operator. Attributes include all characteristics that can be specified for individual dies, e.g., information as to a die to which no special attribute is given, a die to be tested, a marker die, and a preliminary die for a test, information as to types of tests, which groups dies belong to, and a sequence in which a probe goes through dies. However, attributes should not be limited to these items of information.
Since the method according to the present invention makes it possible to manage the data of a plurality of attributes of dies on a semiconductor wafer under a parametric test in a unified manner, and edit and display the data on a real-time basis with one tool. Therefore, an operator who is not highly skilled can easily and reliably specify attributes of dies, such as ones for testing.
Character data and graphical data are displayed simultaneously, and any manipulation of one of the character data and graphical data is reflected in the other data. Therefore, the operator can easily confirm the data. Particularly, character data are arranged in a display sequence in which a wafer prober goes through dies in a test run. When the character data are traced in the sequence, the sequence to go through the dies can be confirmed on the graphical data with the cursor. If data of three values are used, the user may use data of the third value as marker die data or preliminary die data for a die to be tested. Therefore, the values may be signified freely.